Taps

ABSTRACT

This invention relates to a plug and socket type stopcock, notably for use in high vacuum apparatus, in which erosion of the fluorinated hydrocarbon polymer plug is reduced by indenting the plug face around the orifices of the bore through the plug.

O United States Patent 11 1 1111 3,782,686 Cowie Jan. 1, 1974 [54] TAPS3,434,691 3/1969 Hamilton 251/309 x 3,467,356 9/1969 Mueller 251/309 X[75] Inventorf Raymond 2,854,027 9/1958 Kaiser et al... 251/310 xMlddlesborough, England 3,012,752 12 1961 Buck 251 314 x 3,512,9445/1970 Craig et al. 251/309 [73] Assgnee' g Yorksh're 3,415,299 12/1968Hinman, Jr. et a1. 251/309 ux 3,525,363 8/1970 Gore et al 251 309 x [22]Filed: June 19, 1972 3,582,042 6/1971 Gren ier 251/309 264 066 3,678,9607/1972 Le1b1nsohn 251/309 X [2]] Appl. No.:

Primary ExaminerSamuel Scott [30] Foreign Application Priority Data A w-E, F, Wenderoth et a].

June 18, 1971 Great Britain 28,628/71 52 us. c1. 251/309 ABSTRACT 3; Z?This invention relates to a plug and socket type stop- B12 cock, notablyfor use in high vacuum apparatus, in which erosion of the fluorinatedhydrocarbon polymer 56] References Cited plug is reduced by indentingthe plug face around the orifices of the bore through the plug.

9 Claims, 2 Drawing Figures 1 TAPS The present invention relates totaps, notably to stopcocks for use in glass apparatus which is subjectedto high vacuum.

In glass apparatus, the ground glass surfaces of the conventionally usedtapered plug and socket typetwist stopcocks often lock and preventsmooth operation of the stopcock. It has been the practice to grease thestopcock plug to render its operation smooth, but this leads to greasecontamination of material flowing through the stopcock. It has beenproposed to form part or all of the plug from a material with a lowcoefficient of friction, such as polytetrafluorethylene. However, it hasbeen found that the material of the plug surrounding the bore throughthe plug is rapidly eroded away, especially where stopcocks having suchplugs are used in high vacuum apparatus, and that the stopcock fails tohold a high vacuum.

The present invention relates to a form of stopcock plug wherein thiserosion problem is reduced.

Accordingly, from one aspect the present invention provides afluorinated hydrocarbon polymer stopcock plug of generallyfrusto-conical shape having a transverse bore therethrough, the surfaceof the plug being indented at an orifice of the bore to provide aflatted surface around that orifice of the bore.

From another aspect, the invention provides a tapered plug and sockettwist valve wherein the plug is made from a fluorinated hydrocarbonpolymer and has a generally frusto-conical shape, there being atransverse bore through said plug adapted to be placed in register withapertures in the socket wall, the surface of the plug being indented atan orifice of the bore to provide a flatted surface around that orificeof the bore, which surface is of greater dimensions than the diameter ofthe apertures in the socket wall.

The plug and stopcock of the invention are of essentially the samedesign, size and purposes as those in plug and socket type twist valvesused hereto, escept for the flatted surface on the plug.- Desirably,flatted surfaces are provided at each orifice of the bore. Moreover, thebore may be branched or forked to provide a three way twist valve, inwhich case there will be three flats on the surface of the plug.

The flatting of the surface has two effects:

a. by reducing the area of contact between the plug and the wall of thesocket bowl, it increases the contact pressure between the wall and theunflatted portions of the plug thus ensuring a better seal; and

b. by removing material from the orifices of the bore through the plug,the risk of the material at the rim of the orifice being drawn into theapertures in the wall of the socket by cold flow of the plug materialand then nipped off as the plug is rotated is reduced.

In general, the greater the surface of the plug which is indented toprovide the flatted surface, the greater will be these effects. However,it will be appreciated that sufficient unflatted surface of the plugmust remain to close the apertures in the socket wall. In general, it isdesired that each sealing unflatted surface between the indentedsurfaces on the plug measures in all directions at least 1% times thediameter of the aperture in the socket wall it is to seal. Desirably,the tangential dimension of this surface at the level of the socketaperture is not more than about three socket aperture diameters in size,e.g., about two diameters in size. It is preferred that the indentedflatted area extend approximately one half to two, preferably about one,socket aperture radii around the mouth of the socket aperture when theplug bore and the socket aperture are in register. It will beappreciated that the flatted surface must not extend over the wholelongitudinal length of the plug unless steps are taken to seal the plugin the socket. Furthermore, it is preferred that the flatted surface bedisposed substantially symmetrically about the orifice of the plug bore,except where the bore and the socket wall aperture are offset.

The indented surface need not be a flat planar surface, but may berounded as occurs when the indented surface forms a concave dishing ofthe plug surface, when the indented surface is a recessed convex surfaceor when the surface is concave. The term flatted surface is used hereinto denote generically both flat and rounded surfaces. Preferably theindented surface is a substantially flat surface passing through a chordof the cross-section of the plug and lying in a plane substantiallyparallel to the longitudinal face of the plug.

The plugs are made from a fluorinated hydrocarbon polymer having a lowcoefficient of friction and a measure of flexibility so that they deformto compensate for minor irregularities in the socket, which latter ismade for example from glass. Preferred polymers for present use arefluorinated alkene or fluorinated chlorinated alkene polymers, notablypolytetrafluorethylene.

The plugs may be made by any suitable method and the flat surfacesformed on the plug either ab initio or by the subsequent removal ofmaterial from a frustoconical plug. It is preferred to provide thenon-flatted surfaces of the plug with a highly polished surface and thisis conveniently done by a centreless grinding technique.

The socket in which the plug is housed is of conventional type and thebowl is desirably given a highly polished finish. We have also foundthat it is desirable to bell the mouths of the apertures in the socketwall. Where this is done it will be appreciated that the diameter of thewide end of the bell is the diameter of the socket wall aperture to beconsidered when determining the dimensions of the plug to be used in thesocket.

A typical stopcock of the invention will be described by way of examplewith respect to the accompanying drawings, in which:

FIG. 1 is a vertical section view of the plug and socket; and

FIG. 2 is a transverse section through the plug on the line A-A.

The stopcock comprises of frusto-conical socket 1 having diametricallyopposed bell mouthed apertures 2 and 3 in the wall thereof which lead totubes 4 and 5. The socket and tubes are made of borosilicate glass andthe bowl of the socket is ground and polished in the conventionalmanner. Within socket l is located a frusto-conical plug 6 made frompolytetrafluorethylene. The plug 6 is of substantially the same size andshape as the bowl of socket 1 so as to provide sealing engagementbetween the walls of the plug and the socket bowl.

The plug is provided with a T piece top 7 by which it may be rotated inthe bowl' and with a threaded longitudinal extension 8 which carrieswashers 9 and locknut 10 whereby the plug is secured in position andurged into sealing engagement with the socket bowl. The plug is alsoprovided with a transverse bore 11 therethrough which can be placed inor out of register with the apertures 2 and 3 in the socket wall. Thesurface of the plug has been cut away around the orifices of the bore 11 to provide two flatted surfaces in a plane parallel to the face of theplug. As can be seen from FIG. 2 the surfaces may be cut on parallelchords 12 and 13 of the cross sectiion of the plug or be rounded asindicated by the dotted lines. Typically, for a 6 mm radius plug theflatted surface is indented about 0.6 mms into the plug at the centre ofthe chord. The unflatted portions each extend about 2R tangentially andthe flatted indented surfaces extend about 2R longitudinally, R beingthe diameter of the mouth of the apertures 2 and 3. Such a plug iscapable of holding a high pressure differential, even after repeatedactuations.

The above description has been given in terms of a plug having twoflatted surfaces. However, this need not be the case and only oneflatted surface may be provided where the stopcock is to be subjected tocomparatively low pressure differentials. In this case, the stopcock isto be located so that in use the flatted surface of the plug is on thelow pressure side of the stopcock.

In a further modification of the plug of the invention, the upper andlower extremities of the plug are of reduced diameter, e.g., as shown inshading in FIG. 1, to reduce yet further the area of contact between theplug and the socket bowl. This results in an increase in effect (a)referred to earlier.

l claim:

1. A fluorinated hydrocarbon polymer stopcock plug of generallyfrusto-conical shape having a transverse bore therethrough,characterised in that the surface of the plug is indented at an orificeof the bore to provide a flatted surface around that orifice of thebore.

2. A plug as claimed in claim 1 characterised in that the indentedflatted surface is a generally flat surface passing through a chord ofthe cross section of the plug and lying in a plane substantiallyparallel to the longitudinal face of the plug.

3. A plug as claimed in claim 1 characterised in that the upper andlower extremities of the plug are of reduced diameter.

4. A tapered plug and socket twist valve wherein the plug is made from afluorinated hydrocarbon polymer and has a generally frusto-conicalshape, there being a transverse bore through said plug adapted to beplaced in register with apertures in the socket wall, characterised inthat the surface of the plug is indented at an orifice of the bore toprovide a flatted surface around that orifice of the bore, which surfaceis of greater dimensions than the diameter of the apertures in thesocket wall.

5. A valve as claimed in claim 4 characterised in that the indentedsurface on the plug extends around the mouth of the aperture in thesocket wall from one half to two times the radius of the aperture in thesocket wall when the plug bore and the aperture in the socket wall arein register.

6. A valve as claimed in claim 4 wherein each orifice of the transversebore is adapted to communicate with only one aperture in the socket wallat a time.

7. A valve as claimed in claim 4 characterised in that each unflattedsealing surface between the indented surfaces on the plug measures inall directions at least 1 /2 times the diameter of the aperture in thesocket wall which it is to seal.

8. A valve as claimed in claim 5 characterised in that each unflattedsealing surface between the indented surfaces on the plug measurestangentially at the level of the aperture in the socket wall not morethan 3 times the diameter of the aperture in the socket wall which it isto seal.

9. A tapered plug and socket twist valve wherein the plug is made from afluorinated hydrocarbon polymer and has a generally frusto-conicalshape, there being a transverse bore through said plug adapted to beplaced in register with apertures in the socket wall, characterised inthat the surface of the plug is indented at an orifice of the bore toprovide a flatted surface around that orifice of the bore, which surfaceextends around the mouth of the aperture in the socket wall from onehalf to two times the radius of the aperture in the socket wall when theplug bore and the aperture in the socket wall are in register; and inthat each unflatted sealing surface between the indented surface on theplug measures in all directions from l' to 3 times the diameter of theaperture in the socket wall which it is to seal.

1. A fluorinated hydrocarbon polymer stopcock plug of generallyfrusto-conical shape having a transverse bore therethrough,characterised in that the surface of the plug is indented at an orificeof the bore to provide a flatted surface around that orifice of thebore.
 2. A plug as claimed in claim 1 characterised in that the indentedflatted surface is a generally flat surface passing through a chord ofthe cross section of the plug and lying in a plane substantiallyparallel to the longitudinal face of the plug.
 3. A plug as claimed inclaim 1 characterised in that the upper and lower extremities of theplug are of reduced diameter.
 4. A tapered plug and socket twist valvewherein the plug is made from a fluorinated hydrocarbon polymer and hasa generally frusto-conical shape, there being a transverse bore throughsaid plug adapted to be placed in register with apertures in the socketwall, characterised in that the surface of the plug is indented at anorifice of the bore to provide a flatted surface around that orifice ofthe bore, which surface is of greater dimensions than the diameter ofthe apertures in the socket wall.
 5. A valve as claimed in claim 4characterised in that the indented surface on the plug extends aroundthe mouth of the aperture in the socket wall from one half to two timesthe radius of the aperture in the socket wall when the plug bore and theaperture in the socket wall are in register.
 6. A valve as claimed inclaim 4 wherein each orifice of the transverse bore is adapted tocommunicate with only one aperture in the socket wall at a time.
 7. Avalve as claimed in claim 4 characterised in that each unflatted sealingsurface between the indented surfaces on the plug measures in alldirections at least 1 1/2 times the diameter of the aperture in thesocket wall which it is to seal.
 8. A valve as claimed in claim 5characterised in that each unflatted sealing surface between theindented surfaces on the plug measures tangentially at the level of theaperture in the socket wall not more than 3 times the diameter of theaperture in the socket wall which it is to seal.
 9. A tapered plug andsocket twist valve wherein the plug is made from a fluorinatedhydrocarbon polymer and has a generally frusto-conical shape, therebeing a transverse bore through said plug adapted to be placed inregister with apertures in the socket wall, characterised in that thesurface of the plug is indented at an orifice of the bore to provide aflatted surface around that orifice of the bore, which surface exteNdsaround the mouth of the aperture in the socket wall from one half to twotimes the radius of the aperture in the socket wall when the plug boreand the aperture in the socket wall are in register; and in that eachunflatted sealing surface between the indented surface on the plugmeasures in all directions from 1 1/2 to 3 times the diameter of theaperture in the socket wall which it is to seal.